This invention relates to the field of switching devices. The invention is especially useful in the computer and telecommunications fields, although the invention is not limited to any particular area of use.
In a computer installation, it is often necessary to connect one, but only one, of a plurality of computers to a modem, or other hardware device. It is also often necessary to provide a patching connection, whereby an external piece of equipment, such as a substitute or back-up computer, can be connected to one of the main computers.
In the prior art, the above-described objectives have required two independent switching devices. First, one needs a switch which alternately connects one of the computers to the modem line. Secondly, one needs a switch which will automatically break the connection between the computer being serviced and the modem. The devices of the prior art have generally employed two independent switching means for these purposes, and are relatively complicated.
One example of a switching module of the prior art is shown in U.S. Pat. No. 4,112,401. This patent shows a sliding panel on a printed circuit board, the panel being designed to actuate an array of magnetic switches, and thereby to connect and disconnect a plurality of computers from other devices.
Another problem encountered with many switching devices is that one can patch a connection to only one computer at a time. It is often impossible to patch a connection to the equipment which is not being serviced. This inflexibility severely hampers the operation of systems employing a plurality of computers.
Some of the prior art devices have addressed this problem of providing "off-line" access, so as to allow use of the lines which are not currently connected to a computer, for other purposes. An example of a patch module, of the prior art, for providing off-line access, is shown in U.S. Pat. No. 4,237,352. A patching device which makes alternative connections between pieces of equipment, depending on whether and where a plug is inserted, is shown in U.S. Pat. No. 3,588,399. One object of the invention is to provide an improved structure which provides such off-line access.
The present invention provides a module which permits separate patching connections for several computers, wherein all of which connections remain operative whether the computers are "on-line" or "off-line". The invention uses essentially one switching means, which is preferably a slidable panel on a printed circuit board. The initial position of this switching means is controlled by a separate switch, which may be mounted near the panel, or placed in a remote location. The invention maximizes the flexibility of a patch module, because it allows a plurality of diagnostic instruments to be connected to a set of computers, without disrupting the operations of the computers not being serviced.